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<title>Problem 1623. -- [Usaco2008 Open]Cow Cars -- 衡阳八中OJ离线版-2012-02-29</title><center><h2>1623: [Usaco2008 Open]Cow Cars</h2><span class=green>Time Limit: </span>5 Sec&nbsp;&nbsp;<span class=green>Memory Limit: </span>64 MB<br><span class=green>Submit: </span>70&nbsp;&nbsp;<span class=green>Solved: </span>50<br>[<a href='submitpage.php?id=1623'>Submit</a>][<a href='problemstatus.php?id=1623'>Status</a>][<a href='bbs.php?id=1623'>Discuss</a>]</center><h2>Description</h2><div class=content>N (1 <= N <= 50,000) cows conveniently numbered 1..N are driving
in separate cars along a highway in Cowtopia. Cow i can drive in
any of M different high lanes (1 <= M <= N) and can travel at a
maximum speed of S_i (1 <= S_i <= 1,000,000) km/hour.

After their other bad driving experience, the cows hate collisions
and take extraordinary measures to avoid them. On this highway, cow
i reduces its speed by D (0 <= D <= 5,000) km/hour for each cow in
front of it on the highway (though never below 0 km/hour). Thus,
if there are K cows in front of cow i, the cow will travel at a
speed of max[S_i - D * K, 0]. While a cow might actually travel
faster than a cow directly in front of it, the cows are spaced far
enough apart so crashes will not occur once cows slow down as
described,

Cowtopia has a minimum speed law which requires everyone on the
highway to travel at a a minimum speed of L (1 <= L <= 1,000,000)
km/hour so sometimes some of the cows will be unable to take the
highway if they follow the rules above. Write a program that will
find the maximum number of cows that can drive on the highway while
obeying the minimum speed limit law.
</div><h2>Input</h2><div class=content>* Line 1: Four space-separated integers: N, M, D, and L

* Lines 2..N+1: Line i+1 describes cow i's initial speed with a single
        integer: S_i

</div><h2>Output</h2><div class=content>* Line 1: A single integer representing the maximum number of cows
        that can use the highway

</div><h2>Sample Input</h2>
			<div class=content><span class=sampledata>3 1 1 5//三头牛开车过一个通道.当一个牛进入通道时，它的速度V会变成V-D*X(X代表在它前面有多少牛),它减速后，速度不能小于L<br />
5<br />
7<br />
5<br />
<br />
INPUT DETAILS:<br />
<br />
There are three cows with one lane to drive on, a speed decrease<br />
of 1, and a minimum speed limit of 5.<br />
<br />
</span></div><h2>Sample Output</h2>
			<div class=content><span class=sampledata>2<br />
<br />
OUTPUT DETAILS:<br />
<br />
Two cows are possible, by putting either cow with speed 5 first and the cow<br />
with speed 7 second.<br />
<br />
</span></div><h2>HINT</h2>
			<div class=content><p></p></div><h2>Source</h2>
			<div class=content><p><a href='problemset.html?search=Silver'>Silver</a></p></div><center>[<a href='submitpage.php?id=1623'>Submit</a>][<a href='problemstatus.php?id=1623'>Status</a>][<a href='bbs.php?id=1623'>Discuss</a>]</center>﻿<br>

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